Focus responsive exposure control system

ABSTRACT

An exposure control system for a single lens reflex camera. The system incorporates an exposure mechanism having a normally open status for camera viewing and focusing. An exposure cycle is commenced upon energization of a solenoid which drives the exposure mechanism to a closed position. This solenoid is deenergized to commence an exposure interval at which time the blades of the exposure mechanism are driven under spring bias to define a progressively varying exposure aperture. The solenoid is re-energized to terminate an interval of exposure. For flash operation, a second solenoid driven arrangement is provided which selectively inserts a stop within the locus of travel of the blades of the exposure mechanism to arrest their movement under spring bias at an aperture setting automatically selected in correspondence with the focusing adjustment of the camera.

United States Patent [1 1 Eloranta et al.

[ 1 Aug.7, 1973 i 1 FOCUS RESPONSIVE EXPOSURE CONTROL SYSTEM [75}Inventors: Vaito K. Eloranta, Needham;

Edwin K. Shenk, Littleton, both of Mass.

[73 l Assignee: Polaroid Corporation, Cambridge,

Mass.

[22] Filed: Apr. 19, 1971 [21] Appl. No.: 135,211

[52] US. Cl 95/10 CE, 95/10 CT, 95/10 CD,

[51] Int. Cl G031) 7/08, G03b 7/16, G03b 15/05 [58] Field of Search95/10 CE, 10 CT,

95/10 CD, 64 R, 64 A, 64 D [56] References Cited UNITED STATES PATENTS 73,641,889 2/1972 Eloranta 95/l0 CE 3,605,588 9/1971 Ort et al 95/64 RPrimary Examiner-Samuel S. Matthews Assistant Examiner-Russell E. Adams,Jr. Attorney-Brown & Mikulka and Gerald L. Smith 57 ABSTRACT An exposurecontrol system for a single lens reflex camera. The system incorporatesan exposure mechanism having a normally open status for camera viewingand focusing. An exposure cycle is commenced upon energization of asolenoid which drives the exposure mechanism to a closed position. Thissolenoid is deenergized to commence an exposure interval at which timethe blades of the exposure mechanism are driven under spring bias todefine a progressively varying exposure aperture. The solenoid isre-energized to terminate an interval of exposure. For flash operation,a sec ond solenoid driven arrangement is provided which selectivelyinserts a stop within the locus of travel of the blades of the exposuremechanism to arrest their movement under spring bias at an aperturesetting automatically selected in correspondence with the focusingadjustment of the camera.

50 Claims, 7 Drawing Figures mum mu SHEET 1 0F 4 WWW Ms Nwm n EE nO MKKI R mm M V M PATENTEI] AUG 7 I975 SHEEI 2 [IF 4 TM m m Nw H E E s N N xM A wt PATENIEUAUG Hm SHEET 3 BF 4 I l I l lll/4lllllllll'lli INVENTORSVAITO K. ELORANTA BY EDWIN K. SHENK m mm ma! Mas a ATTO NEYS FOCUSRESPONSIVE EXPOSURE CONTROL SYSTEM BACKGROUND OF THE INVENTION Whenoperated in conjunction with flash or transient illumination, theexposure mechanisms of photographic cameras typically are adjusted inaccordance with the levels of illumination anticipated at a subjectbeing photographed. To anticipate these levels, photographcrs generallyturn to an analytic lighting evaluation derived from the characteristicsof the flash light source. This approach fundamentally is based upon anapplication of the inverse square law for light energy propagation.Under this law, the light energy available from a given source isconsidered to vary inversely with the square of the distance from thatsource. For any given photographic situation, a photographer makes useof the law by initially determining the light sourceto-subject distance;then, by simple computation, this distance is factored into a referenceor guide number correlating light energy with distance, lens andreflector characteristics and film sensitivity to evolve anilluminational factor or exposure value. The camera exposure mechanismis then manually adjusted to a conformance with the pre-computedexposure value. This adjustment is generally carried out through anappropriate exposure aperture setting.

In some camera designs, exposure control adjustment for flash operationis effected semi-automatically by incorporating within the apparatuswhat is termed as a follow-focus mechanism. With a follow-focusarrangement, aperture adjustment or a flash illumination output controlis mechanically coupled with the range findingflor focusing system of acamera.

For many applications, the adaption of conventional photographicaperture mechanisms to semi-automatic follow-focus operation is notsimply carried out. As it becomes more and more desirable to constructcameras in thin and compact configurations suited to be carriedconveniently within a pocket of a garment, a provision for dual exposureregulating systems becomes difficult to realize with acceptable designefficienciesv and economies. This dualism requirement stems from theabove-discussed different basis upon which scene lighting is evaluatedfor flash as opposed to ambient or daylight illumination. Particularlywhere aperture is adjusted as a follow-focus procedure, the exposurecontrol housing of a camera must incorporate one aperture adjustmentmechanism for daylight regulation as wellas a second adjustmentmechanism which is operative only during flash illuminat ed exposures,which is mechanically coupled with the focusing system of the camera,and which otherwise does not interfere with the daylight or ambient modeexposure regulating system. An incorporation vof such dual regulationsystems within fully automated but thin and compact cameras presentseven more severe design considerations.

Such automated cameras should perform automatically in a flash mode uponthe mounting of a flash illuminating unit and should return to normalambient mode operation automatically upon the ,demounting of suchilluminating units. The follow-focus components of the exposure controlsystem must be so designed as not to interfere with operation of thecomponents of the ambient lighting exposure control apparatus.

In one fully automated but thin and compact camera described in a U. S.Pat. No. 3,641,889 entitled, Exposure Control System" by Vaito K.Eloranta, an exposure control system is provided wherein both apertureand exposure interval are automatically varied in accordance with scenelighting conditions. Additionally, this exposure control system operatesin conjunction with a single lens reflex viewing system as well as amotorized automatic film processing arrangement. Exposure regulationwithin the thin, compact camera takes place as part ofa multi-stepprogram involving theconversion of an optical path between viewing andexposure operational modes. As part of this program, the exposuremechanism ofthe camera initially operates in a relaxation mode whereinthe shutter-aperture blades thereof are normally fully open at maximumaperture to permit optimum viewing and focusing of a photographicsubject. Following the depression of a start or actuator button, theexposure mechanism is converted to a driven mode wherein the opticalpath of the camera is fully blocked as a reflex operator assembly ismoved into its exposure position. Following an appropriate delaysufficient to permit the camera to convert to its exposure mode, theexposure mechanism is converted to a relaxation mode during whichexposure is automatically controlled in accordance with ambient scenelighting. An exposure interval is terminated by the return of theexposure mechanism to its driven mode to close the optical path. Thismode is sustained while the reflex operator assembly is returnedto itsviewing mode orientation. Additionally, a film unit, exposed duringtheexposure interval, is automatically driven through a processing station.Following a resumption of a viewing operational mode, the exposuremechanism is returned to itsv relaxation mode.

A follow-focus system for such a camera requires that the exposuremechanism provide for aperture ad justment in accordance with subjectrange when the camera is operated in conjunction with a flash source ofillumination. Further, the camera must automatically convert to flashmode performance upon the mounting thereon of a flash unitqAdditionally,flash mode performance of the exposure mechanism must be provided underdesign criteria in which the exposure system is capable of operatingwithin the complex program logic of the reflex camera and does notconflict with its operation under ambient lighting conditions.

' .SUMMARY OF THE INVENTION The invention now presented offers a fullyautomatic exposure control system having follow-focus capability. Ofparticular merit, this system readily provides for a range responsiveaperture adjustment withinthe extremely limited confines of a thin,compact photographic camera suited for facile carrying within the pocketof a garment.

As an-added feature, the exposure control system of the invention isautomatically convertible to flash mode operation upon theremovablemounting of a flash unit upon a camera within which it is incorporated.

The follow-focus feature of the exposure system of the invention isuniquely actuated during a photographic cycle through the use of anelectromagnetically driven arrangement present in the form of asolenoid. When selectively actuated, resulting from the attachment ofthe flash unit upon the apparatus, the solenoid driven follow-focusarrangement causes an. exposure mechanism to establish an aperture valueover the optical path of the camera corresponding to the focusing orrange adjustments of the taking lens thereof. During daylight operationof the camera, this range responsive aperture adjusting feature is bothinoperative and fully isolated from the normal ambient operation of theautomatic exposure control system.

Another feature and object of the invention is to provide an exposurecontrol system for photographic apparatus incorporating an exposureregulator arrangement having a driven mode effective to block thepassage of light along the optical path of the apparatus and arelaxation mode effective to progressively unblock this path to derive apredetermined aperture variation thereover. The exposure control systemincorporates a solenoid drive arrangement which is adjustable inaccordance with the focus adjustment of a taking lens of the apparatus.Through selective energization of this solenoid drive arrangement, theexposure regulator arrangement can be intercepted in its relaxation modeto cause it to operate in a follow-focus manner.

A further feature and object of the invention is to provide afollow-focus exposure control system for a single lens reflex camera,the optical path of which is altered by a reflex operator assembly forpurposes of converting the camera from a viewing mode to an exposuremode. The control system incorporates a shutter-aperture exposureregulating assembly wherein two mutually coactive blades are selectivelydriven by a solenoid into a position blocking the optical path of thecamera. Exposure regulation is provided by releasing the blades fromthis blocking position to define progressively varying values ofexposure aperture over the optical path. The shutter-aperture is drivenby the solenoid into a blocking position during those intervals of aphotographic cycle wherein the reflex operator assembly is moved betweenits operative positions. Through the use of a second solenoid drivenassembly, an arrangement is provided for intercepting the exposureregulator assembly during movement from its blocking position to providea focus related aperture adjustment during flash illuminated exposures.By selectively de-energizing this second solenoid during a photographiccycle, the shutter-aperture regulator arrangement is permitted to returnto its normal or daylight operation at such time following an exposureinterval when the reflex operator assembly is returned to a viewing modeposition.

Because of the relative simplicity of the exposure control system of theinvention, it readily may be incorporated within cameras of thin,compact design. Because of the technique utilized in establishing afocus related aperture adjustment with the system, it is readilyincorporated within fullyautomated single lens reflex cameras havingsomewhat detailed or complex operational programs.

Other objects of the invention will become apparent in the course of thedescription to follow.

The invention accordingly comprises the system and apparatus possessingthe construction, combination of elements and arrangement of parts whichare exemplified in the following detailed disclosure.

For a fuller understanding of the nature and objects ofthe invention,reference should be had to the following detailed description taken inconnection with the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a side elevational view of asingle lens reflex camera of a type within which the exposure system ofthe invention may be incorporated, portions of the figure being brokenaway or shown in phantom to reveal internal structure;

FIG. 2 is a front sectional view of the exposure housing the camera ofFIG. 1 with portions removed to reveal the internal structure;

FIG. 3 is a side view of the exposure housing of FIG.

FIG. 4 is a fragmentary view showing select compo: nents of the exposuremechanism of FIG. 2 in enlarged detail;

FIG. 5 is a front sectional view of the exposure housing of a camera ofFIG. 1 showing certain components of its exposure mechanism as theyassume an orientation blocking the optical path of the camera;

FIG. 6 is another view of the orientation of components shown in FIG. 5,but at an intermediate stage within a photographic cycle; and

FIG. 7 is a circuit diagram illustrating a control arrangement for usewith the exposure control system of the invention.

DETAILED DESCRIPTION OF THE INVENTION The exposure control system of thepresent invention is ideally suited for incorporation within a fullyautomated single lens reflex camera. To perform in reflex fashion, thesecameras incorporate a reflex operator assembly which is normallyretained in a viewing mode orientation permitting a scene to be framedand focused at a viewing surface formed within or upon the assembly. Toderive adequate lighting for purposes of viewing and focusing thecamera, the exposure control system thereof maintains a full apertureopening and open shutter until the camera is actuated to commence aphotographic cycle. When the camera is so actuated, the shutter is fullyclosed to secure its exposure chamber while the reflex operator assemblyis moved into its exposure orientation. Once converted for exposure modeoperation, an exposure is made following which the shutter is again heldfully closed while the reflex operator assembly is returned to itsinitial viewing mode orientation. As this orientation is again reached,maximum aperture width is again established and the shutter is permittedto open to provide for viewing and focusing in preparation for asubsequent photographic cycle.

Referring to FIG. 1, a single lens reflex camera, suited to incorporatethe exposure control system of the invention, isdepicted generally at10. Camera I0 is of a foldable variety and is formed of a combination ofinter-linked walls and housing members which are pivotally collapsiblein to a rectangular base or housing structure 12. For instance, thestructure of camera 10 includes an elongated top wall 14 which is hingedto the rearward top portion of base 12. Wall 14 is hinged at itsuppermost edge to a shorter forward wall 16 which, in turn, is hinged tothe upper surface of an exposure housing 18. Exposure housing 18 ispivotally attached to the forward portion of base 12 so as to nesttherewithin when the camera 10 is folded for carrying.

In the erected position shown, exposure housing 20 positions thecentrally disposed optical objective or taking lens assembly of thecamera in a position appropriate for making an exposure. Positionedappropriately across this optical path is an exposure regulatingmechanism including a shutter-aperture assembly along with the controlcomponents of the exposure system of the camera. Among these controlcomponents are a start button22, a light sensing entrance assembly 24, afocus adjusting wheel 26 and a flash unit supporting platform 30.Platform 30 is configured to support a packaged linear multilamp flashassembly as at In the erected configuration of the camera as shown, rearwall 14 is supported by erecting linkages as at 34. The interconnectionof rear wall 14, top wall 18, and exposure housing 20, serves to providean exposure chamber 36, the lighttight integrity of which is provided bya flexible opaque bellows, a fragment of-which is shown at 38.

Base 12 is configured at the bottom of exposure chamber 36 to receiveand support a disposable film retaining cassette structure, a side ofwhich is shown at 44. Cassette structure 44 is of rectangularconfiguration and retains a stacked array of discrete film units, theuppermost one of which is positioned in coincidence with the exposureplane of the camera 10. This plane is positioned just beneath arectangular opening or film frame defined within a ridge 46 formedwithin the upper surface of cassette structure 44. Cassette 44 alsocontains a flat battery power supply in its lowermost portion whichcommunicates with terminals (not shown) within the base 12.Additionally, the forwardmost peripheral side of cassette 44 is formedhaving an egress opening or slot through which the uppermost film unitautomatically is' removed for processing following its exposure. Filmunits suited for use with the camera 10 are described in detail ina'patent by E. H. Land, US. Pat. No. 3,415,644, entitled, NovelPhotographic Products and Processes." In the orientation shown in FIG.1, the components of camera 10 provide for its operation in a viewingmode in which framing and focusing are carried out by the operator. Inthis configuration, a reflex operator assembly 50 is retained in aspring-loaded or cocked orientation over the ridge 46 of cassette 44,blocking the passage of light through the film frame defined thereby.Operator assembly 50 is configured on one side to support a viewingsurface 52 which faces into the exposure chamber 36 during viewing andfocusing procedures. Assembly 50 supports a mirror or similarlyspecularly reflecting surface 54 upon its somewhat flat surface oppositeviewing surface 52. The operator assembly 50 is coupled to the rear ofbase 12 by hinges at 56 positioned at each side of the rearward edgethereof. When in a viewing operational mode, camera 10 establishes anoptical path extending from its taking or objective lens system withinexposure housing to a mirror or specularly reflecting surface 60 fixedwithin theexposure chamber 36 to the inward side of rear wall 14, thenceto the viewing surface 52 upwardly facing from operator assembly 50.Viewing surface 52 is configured having a texture and optical designfacilitating the focusing of the image of a scene to be photographed.This image may be viewed by the camera operator through an opticalentrance assembly 62 centered and mounted upon top wall 18. Aconfiguration suited for viewing surface 52 is described and claimed ina copending US. Pat. application Ser. No. 83,030, filed Oct. 22, 1970,by Nathan Gold, entitled Reflective Imaging Apparatus," and assigned incommon herewith. Optical entrance assembly 62 and its related internalcomponents are described in detail in a copending U.S. Pat. applicationSer. No. 98,356 by James G. Baker, filed Dec. 15, 1970, entitled, ReflexCamera and Viewing Device, and assigned in common herewith.

The components of camera 10 normally assume a configuration foroperation in a viewing mode wherein focusing can be carried out byoperator manipulation of focusing wheel 26. During a photographic cycle,however, the components are re-oriented to assume an exposure modeconfiguration. FIG. 1 of the drawings is arranged as such that theoperator assembly 50 is illustrated in solid line fashion at itsfocusing mode orientation, while its alternate exposure mode orientationis shown in phantom at 50. Assembly 50 is retained in its viewing modeorientation against ridge 46 of cassette 44 by a four-bar linkage showngenerally at 64. Linkage 64 includes a first lever portion formed aspart of hinge 56 which is pivotally connected at 66 with a draw-downlink 68. Draw-down link 68, in turn, is pivotally connected at 70 to acrank linkage 72. Crank linkage 72 is coupled to a spring driving systemat 74 as well as to a motor driven cocking mechanism through a drivecrank 76. One end of a motor providing power for the latter cockingsystem is shown at 80. The four-bar linkage 64 as well as its relateddriving components are described in detail in a co-pending US. Pat.application Ser. No. 134,733, entitled, Reflex Camera, by E. H. Land, I.Blinow and V. K. Eloranta, filed Apr. 16, 1971, and assigned in commonherewith.

During a viewing mode of operation, the exposure control system ofcamera 10 provides for an open shutter condition with widest availableaperture. Following the depression of start button 22, the exposuremechanism of the camera blocks the optical path and operator assembly 50is spring driven fromfour-bar linkage 64 to rotatably rise into theposition illustrated at 50' adjacent mirror 60 at rear wall 14. Thismaneuver serves to unblock the exposure plane outlined by ridge 46 ofcassette 44 and, additionally, to introduce mirror surface 54 into theoptical path of the camera at position 54'. In an exposure mode, theoptical path of the camera I0 extends from the taking objective thereofwithin exposure housing 20 to mirror surface 54, thence to the uncoveredexposure plane of the camera.

Following the assumption by operator assembly 50 of its exposure modeorientation 50?, the exposure mechanism of the camera cycles through anexposure inter val, whereupon it again blocks the optical path of thecamera to permit the operator assembly 5 0 to be driven from motor 80and crank 76'into its viewing mode orientation. During this cockingmaneuver, an exposed film unit is withdrawn from cassette 44 andintroduced into 'a processing station shown generally at 92. Pro

cessing station 92 is formed of two pressure applying rolls, 94 and 96.These rolls are driven frommotor through a gear train, one component ofwhich is shown as a drive gear 98. Gear 98 is meshed with a driven gear100 coupled with upper roll 94. The details of the gear train, includinggears 98 and 100 as well as their driving connection with motor 80, aredescribed in detail in the above-noted application for United StatesPatent by E. H. Land et all From the foregoing, it will be apparent thatautomatic operation of the camera 10 requires an exposure mechanismincluding shutter and aperture control which must accommodate to thesomewhat involved mechanical logic involved in converting back and forthbetween a viewing mode and an exposure mode of oporation. For instance,at the commencement of an exposure cycle, the exposure mechanism of thecamera must be opened to provide widest possible aperture. As theshutter release button 22 is depressed, the exposure mechanism mustblock the optical path while operator unit 50 rises under spring bias toits exposure mode orientation at 50. The exposure control mechanism mustthen again open to expose an uppermost film unit at the exposure planeof the camera. This exposure preferably is carried out under apredetermined program relating optimum exposure interval and aperturevalues with scene light level. Alternately, the exposure mechanism mustoperate in a follow-focus manner in which aperture values areestablished in accordance with the light levels anticipated from flashunit 32. Following an exposure interval for both ambient and flashoperation, the exposure mechanism must be held in its light blocking orclosed position, while the operator unit 50 is driven to its downwardposition blocking the passage of light through the film frame 46 to theexposure plane of the camera. When the operator unit 50 is in this lightblocking viewing mode position, the exposure mechanism must again beopened to establish maximum aperture.

While performing under the logic criteria outlined above involvingalternate performance for ambient or daylight operation as well as forflash operation, any exposure control mechanism should be of anon-complex mechanical design suited to high-volume productiontechniques. The exposure control mechanism of the present inventionmeets such criteria.

Referring to FIGS. 2 and 3, the exposure mechanism is illustrated incloser detail. As shown generally at 104, the exposure mechanism isformed having two cooperatively moving shutter-aperture blades, 106 and108, which ride transversely within supporting track 109 formed withinexposure housing 20. Each of the blades, 106 and 108, is formed having aselectively shaped aperture opening, respectively depicted at 110 and112, which are movable across the optical path of the. camera in thevicinity of the objective or taking lens positioned with respect to anaperture or optical path entrance at 114. Depending upon the position ofblades 106 and 108, aperture openings 110 and 112 symmetrically overlapover the entrance 114 of the optical path of the camera 10 to defineselectively varying aperture sizes. Each of the blades, 106 and 108, isadditionally configured having a selectively configured andcorresponding photocell sweep opening, respectively depicted at 118 and120. Openings 118 and 120 are con-. figured respectively incorrespondence with the contours of aperture openings 110 and 112. Theopenings 118 and 120 move with mutual symmetry over a small fixedaperture 122 providing for a passage of light from the scene beingphotographed to the photosensing element of a light sensitive controlcircuit.

Blades 106 and 108 define a progression of apertures over opening 114 asa result of their connection with a walking beam as shown at 124.Walking beam 124 is formed having a centrally disposed driving hub 126which is journaled for rotation over an upstanding stud 128 fixed, inturn, to exposure housing 20. Elongate slots as at 130 and 132 areformed in the outward tip portions of beam 124 for the purpose ofproviding connection with pins 134 and 136 extending, respectively, fromblades 106 and 108. Thus interconnected, the blades 106 and 108 movesimultaneously and in correspondence with each other to define asymmetrically configured variable aperture opening over the cameraoptical path 114 as well as over the photocell aperture 122. Elongateslots and 132 serve the function of accommodating the horizontallyrestricted movement of blades 106 and 108 along a cord through the locusof rotation of the tips of beam 124. Beam 124 is biased by a spirallywound spring 138. The movable end of spring 138 is attached to pin 136of blade 108, while its stationary end is affixed to a stud 140extending from exposure housing 20. With this connection to spring 138,the exposure mechanism is biased for movement into a normally openorientation when in its relaxation" mode of operation.

The exposure control system of camera 10 also includes an exposuremechanism electromagnetic drive, including a solenoid 144. Mountedwithin exposure housing 20 by bracket 146, solenoid 144 is ofconventional design, having an internally disposed cylindrical plunger148 which retracts inwardly into the body of the solenoid 144 uponenergization thereof. Plunger 148 is connected with walking beam 124 bya flexible cable 150. One end of cable 150 is connected to a bolt 152threadably inserted within the central portion of plunger 148. A locknut 154 retains bolt 152 in appropriate position. The opposite end ofcable 150 is con nected by a bolt 156 to the outer periphery of drivinghub 126 of walking beam 124. Outward travel of the plunger 148 resultingfrom tension exerted from spring 138 through cable 150 is limited by astop portion 158 of bracket 146.

In its normal or relaxed condition, the exposure mechanism assumes theconfiguration of FIGv 2 wherein blades 106 and 108 define a maximumope'ning over aperture 114 as well as over photocell aperture 122. Inthis condition, solenoid 144 is not energized and walking beam 124 holdsthe blades 106 and 108 in the position shown by virtue of the rotationalbias exerted by spring 138. Energization of solenoid 144 causes plunger148 to rapidly withdraw into the body of solenoid 144. Asa consequence,hub 126 is rotated from cable 150 and walking beam 124, in turn, isrotated into the orientation illustrated in FIG. 5. The extent of thisrotation is limited by a contact pin 164 ex tending from exposurehousing 20. In this orientation, entrance opening 114 of thetaking lensoptical path of the camera is completely closed. A subsequentdeenergization of solenoid 144 releases plunger 148 and allows beam 124to rotate under thebias exerted by spring 138. This rotation pennitsopenings 110 and 112 of respective shutter blades 106 and 108 to definepro'-.

gressively enlarging apertures as they move toward a terminal positionlimited by a pin 162 (FIG. 2). Simultaneously with this movement,openings 118 and 120 define a correspondingly progressively enlargingaperture over the photocell opening at 122. When detection circuitryassociated with the photocell located at opening 122 develops anappropriate exposure terminating signal, solenoid 144 will again beenergized to retract plunger 148. A retraction of plunger 148 causesshutter blades 106 and 108 to resume the closed positions shown in FIG.5. Following an interval required for the camera to re-assume itsviewing mode orientation, the solenoid 144 is deenergized to permitblades 106 and 108 to assume the maximum aperture position of FIG. 2.

With the exposure control arrangement t'hus' disclosed, for daylight orambient illumination, dual exposure parameter control is achieved withrelative simplicity while providing for a shutter operation within theprocess logic requirements of the form of single lens reflex cameradescribed in connection with FIG. 1. The exposure mechanism further iscapable of performing in follow-focus manner for flash illuminationthrough the use of a small, relatively low-power electromagneticallydriven assembly.

For flash operation, the exposure mechanism of the invention providesfor aperture regulation in correspondence with the focus setting of thetaking lens of the camera. The taking lens system of the camera ismounted within an externally threaded cylindrical bezel assembly, theouter threaded periphery of which is shown at 170. A detaileddescription of such a lens mount is described in a copending U.S. Pat.application Ser. No. 101,745 by Rosario J. Messina, entitled AdjustableLens Mounting, filed Dec. 28, 1970, and assigned in common herewith.Bezel 170 is rotatable to provide objective lens focusing. Manual drivefor this rotation is provided from the externally threaded focusadjusting wheel 26. Referring additionally to FIG. 3, driving connectionbetween focus adjusting'wheel '26 and bezel 170 is provided by an idlergear 172 mutually meshed therebetween. As is apparent, with theinterconnection of bezel 170 and focus wheel 26, the rotationalorientation of focus wheel 26 corresponds with the focus settingof thelens system within bezel 170.

This rotational correspondence of focus wheel 26 is selectively andcontrollably introduced into the exposure mechanism through selectiveenergization and adjustment of a second, follow-focus solenoid drivenarrangement including a solenoid 174. Solenoid 174 is moved incorrespondence with the focus setting of wheel 26 to positions at whichit can intercept and arrest the rotation of walking beam 124 during itsrelaxation mode travel under the bias of spring 138. Accordingly,solenoid 174 is coupled through a bracket 176 to a rack and pinionassembly including rack 178 and a pinion gear 180. As illustrated indetail in FIGS. 3 and 4, rack 178 is slideably mounted upon abase plate182 and bracket 184 fixed within exposure housing 20. The rearwardlyextending portion of rack 178 isgeared at 186 in conventional fashion tomesh appropriately with pinion,l80. Pinion 180 is-rotatably mountedwithin housing 20v so as to mesh with an inwardly facing internal ringgear'l88 formed within the inwardly facing sides'of focuswheel 26. Thusinterconnected with focus wheel 26, solenoid 174 is movable laterallyalong the locus of travel of the upward side of walking beam 124 incorrespondence with any given focus setting of wheel 26.

Follow-focus solenoid 174 is configured having a plunger 192 which isbiased to retract inwardly away from the locus of travel of beam 124 bya spiral spring 194 wound thereabout and positioned between a rearwardcap on plunger 192 and bracket 176. The forward end of plunger-192 isconfigured to form a detent as at 196.

When energized, solenoid 174 extends plunger 192 such that it interceptsand arrests the movement of walking beam 124. Interception is effectedalong one edge of a thin extension 200 of beam 124. Detent 196 ispresent to provide a capture function such that once the beam 124 iscontacted by plunger 192, solenoid 174 may be de-energized while plunger192 remains extended to arrest beam 124. During ambient operation of theexposure control system, solenoid 174'remains de-energized and spring194 retains plunger 192 along with its detent tip 196 in retractedposition such that no contact and resultant interference is made withthe movement of walking beam 124. Accordingly, no interference ispossible between the flash or followfocus and ambient or daylightcomponents of the exposure system. I

During a photographic cycle in which flash illumination is utilized, theflash exposure control system is armed and a photographic cyclecommences with the energization of solenoid 144 and the closure ofblades 106 and 108 as shown in FIG. 5. When the blades 106 and 108 blockthe optical path at 114 and operator assembly 50 is moved into itsexposure mode orientation as shown at 50 in FIG. 1, solenoid 144 isde-energized to release walking beam 124 for movement under the bias ofspring 138. Prior to this de-energization, solenoid 174 is energized tocause plunger 192 to be extended into the pathsof travel of beamextension 200. Note that energization of solenoid 174 will take place aswalking beam 124 is in its terminal position, extension 200 contactingpin 164. Accordingly, no interference is possible between the extendedplunger 192 of energized solenoid 174 and walking beam 124. In ac-'cor'dance with normal ambient operation of the exposure mechanism,solenoid 144 is then de-energized to release walking beam 124 formovement under the bias of spring 138. This movement is limited,however, by the position of the extended plunger 192. When extension 200contacts plunger 192, an aperture will be defined by blades106 and 108which corresponds with the position of solenoid 174,.and, accordingly,with the focal setting of taking lens of the camera 10. Following aninterval of time sufficient for walking beam 124 to move from itsterminal position contacting pin 164 to its terminal position contactingpin 162, solenoid 174 is de-energized and a flashlamp simultaneously isfired. De-energization of solenoid 174 does not release the contactbetween plunger 192 and beam extension 200 with this d'e-energizationinasmuchas detent 196 will have captured extension 200.-A typical:intermediate aperture setting provided by the system is illustrated inFIG. 6, while the above-described capturing off the plunger 192 throughthe use of detnet 196 is illustrated in more detail in connection withFIG'. 4

An exposure is terminated upon the, re-energization of solenoid. 144which causes plunger 148 'to be re tracted and beam 124 to berotated-from cablelll50 to drive blades 106 and 108 to the closedposition shown in FIG. 5. As extension 200 isrotated toward pin 164, thecapture between detent 196 and extension 200 is released. Following thisdisengagement, plunger 192 of solenoid 174 is permitted to return to itsretracted position out of contact with beam 124 as a result of biasexerted from spring 194. During the ensuing closed status of theexposure mechanism, operator assembly 50 is moved from its exposure modeorientation 50' into its viewing mode orientation as shown in FIG. 1-at50'.

Note that with the arrangement thus described the exposure mechanism ofthe invention is capable of operating in either a follow-focus orambient mode using a simple mechanism and without interference'betweenthe two exposure regulating systems.

lines 212 and 214 initially enables a mode conversion timing function218 from along lines 220 and 222. Conversion timing function 218includes an R-C timing net work and triggering circuit such as adifferential comparator and is activated in conjunction with themovement of operator assembly 50. In this regard, the output 224 oftiming function 218 remains at the ground potential of power line 214until such time as the operator assembly 50 reaches its exposure modeconfiguration. For purposes of facilitating the description to follow,when the outputs of such triggering systems or comparators are at theground reference potential of line 214, they are referred to as low andwhen they assume the voltage status of source line 212, they arereferred to as being high. Output 224 is coupled through a diode 226,bias resistor 228 and line 230 to the base electrode of a PNP transistorQ.,. The emitter of transistor Q is coupled through a line 232 to powerline 212 and its collector is connected with a secondary or logic powerline 234. The low" status at output 224 of mode conversion timingfunction 218 at the commencement of a photographic cycle serves toforward bias the base-emitter junction of transistor Q thereby poweringlogic power line 234 from power line 212.

Energization of logic power line 234 from transistor Q serves initiallyto energize the exposure mechanism solenoid 144 by forward biasing thebase-emitter junction of an NPN transistor Q Forward biasing current isdirected to the base of transistor 0,, from line 234 through a line 236,bias resistor 238, diode 240 and diode 242. The emitter of transistor iscoupled to reference power line 214, while its collector is coupled topower line 234 through line 244 including resistors 246 and 248. An onstatus at transistor O in turn, forward biases the base-emitter junctionof a PNP transistor Q the base of which communicates with reference line214 through transistor Q resistor 246, line 244 and line 250. Theemitter of transistor 0;, is connected with power line 234 and itscollector isconnected along a line 252 through resistors 254 and 256 toground reference line 214. Conduction through line 252,,an turn, forwardbiases the base-emitter junction of an NPN transistor 0,, the base ofwhich is connected to line 252 through line 258. The emitter oftransistor is coupled to ground reference line 214, while its collectoris connected through the winding 260 of solenoid 144 to main power line212. Solenoid 144 is depicted functionally in FIG. 7 by a dashedboundary.

The time interval required for solenoid 144 to cause exposure mechanism104 to close and thereby secure exposure chamber 36 is followed by anR-C' timing network 264 comprised of resistor 266 and a capacitor 268operating in conjunction with a differential comparator 270.Differential comparator 270 is coupled to logic power line 234 fromalong line 272, and to ground reference line 214 from along line 274;The comparator 270 is of conventional design, operating-as anoninverting amplifier. The output of comparator 270 at line 276 mayassume a high" or low status in response to the receipt at its inputline 278 of a voltage signal, respectively, above or below apredetermined reference level. This signal is derived from the R-Ctiming network 264. Input 278 of differential comparator 270 is coupledto line 280 at a point within network 264 intermediate resistor 266 andcapacitor 268.

Timing network 264 is designed having a time constant selected to reachthe trigger level of differential comparator 270 in a period of timecorresponding to the time required to assure that the blades 106 and 108of exposure mechanism 104 have moved from a fully open position to afully closed position. During this timing interval, the output at line276as'sumes a low" status. Timing operation of the network 264 ispermitted as a result of the of status of an NPN transistor 0 Thecollector of transistor O is coupled to line 280 intermediate resistor266 and capacitor 268, and its emitter is connected through line 282 toground reference line 214. Thus connected, transistor 0 is used toselectively shunt capacitor 268 and reset network 264. To forward biastransistor 0 and thereby shunt capacitor 268, biasing current issupplied to the base thereof from logic power line 234 through line 284,bias resistor 286, line 288 and diode 290. At the commencement of anexposure interval, however, this current is diverted through a diode 292across a closed switch 294 to'ground reference line 214. Switch 294 is aphase cycle switch which is actuated simultaneously with the movement ofoperator assembly 50 into or out of its viewing mode position. Untiloperator assembly 50 is released for movement from its cocked position,switch 294 remains closed. 7

When timing network 264 achieves the threshold or reference voltage ofcomparator 270 following a period of time adequate to permit solenoid144 to fully close blades 106 and 108, the output at line 276 goeshigh." A high output at line 276 terminates a clamping current flow fromlogic power line 234 into line 296, bias resistor 298 and output line276 of differential comparator 270. As a result, current now passesthrough diode 300 to forward bias the base-emitter junction of an NPNtransistor Q The emitter of transistorQ, is connected with powerreference line 214 and its collector is connected with power line 212through a line 302 including bias resistors 304 and 306. As current isconducted through transistor Q the base-emitter junction of a PNPtransistor Q is'forward biased. The base of transistor Q, is coupled toline 302 intermediate resistors 304 and 306, while its emitteris'coupled to power line 212. The collector of transistor 0 is coupledalonga line 308 which, in turn, is connected to the terminals ofa d.c.motor 310 and with ground reference line 214. Motor 310 corresponds withmotor of camera 10. With the forward biasing of transistor 0,, motor'3l0is energized briefly and, through anappropriate latching mechanism,releases operator assembly 50 for movement under spring drive to itsexposure mode position. An appropriate mechanism for providing such amotor actuated latching function is described in detail in theabove-referenced application for US. Pat. by E. H. Land et al. As theoperator assembly 50 leaves its cocked orientation, switch 294 is openedto deenergize motor 310 and activate mode conversion timing function218.

This initial de-energization of motor 310 is carried out by there-assertion of a forward biasing current flow along line 284, throughbias resistor 286, line 288 and diode 292 to the base of NPN transistorQ With the opening of the phase cycle switch 294, this forward biasingcurrent is no longer diverted through diode 292 and the switch 294. As aconsequence, timing capacitor 268 of timing network 264 is shunted toground reference line 214 through line 282. With the shunting ofcapactior 268, the output at line 276 of differential comparator 270goes low" and current at line 296 is diverted from the base oftransistor Q The diverting path includes output line 276 and thecomparator 270. As a consequence, the forward bias exerted at transistorO is removed and conduction through line 302 is terminated. As a result,the forward bias at transistor O is removed and motor 310 isde-energized.

Early in a photographic cycle, while switch 294 is closed, the timingoperation of mode conversion timing function 218 is restrained by acurrent diverting clamp including line 314, diode 316, line 318 andswitch 294. Line 318 is connected between logic power line 234 andreference level power line 214 and includes a current limiting resistor320 and diode 322 as well as switch 294. With the opening of switch 294,line 314 no longer communicates with ground reference line 214 throughline 318, and function 218 is permitted to commence timing the periodrequired for operator assembly 50 to move from its viewing modeorientation into its exposure-mode orientation.

An opening of switch 294 also permits the forward biasing ofthebase-emitter junction of an NPN transistor Q The base of transistor O isconnected with logic power line 234 through a line 324 including diode326 and a bias resistor 328. Current flow through line 324 is divertedthrough line 330 and diode 332 into line 318 whenever switch 294 isclosed. Accordingly, with the closure of switch 294, transistor 0,, isoff." The emitter of transistor 0 is coupled to ground reference line214, while-its collector is connected through resistor 228 and line 230to the base of transistor Q,. A latching arrangement is provided therebywhich serves to hold transistor Q on as long as switch 294 remains openduring a photographic cycle.

The opening of switch 294 de-activates another clamping arrangementincluding line 334 which extends through a diode 336 and bias resistor338 to logic power line 234. Coupled to line 334 at a point intermediatediode 336 and bias resistor 338 is a line 340 incorporating diodes 342and 344 and extending to the base of an NPN transistor Q The emitter oftransistor Q, is connected to ground reference line 214 and itscollector is connected through line 346, bias resistor 348 and line 350to the base of a PNP transistor Q10. A resistor 352 is'connected in line346 between line 350 and logic power line 234 to provide turn-off" biasat transistor 0, The emitter of transistor Q is connected to logic powerline 234 and its collector is connected with an exposure function powerline 356.

Transistors Q and Q being thus interconnected, when transistor O isforward biased by current from line 340 through diodes 342 and 344,conduction to ground line 214 will be completed and the base-emitterjunction of transistor Qro will be forward biased. However, when switch294 is closed, current otherwise forward biasing transistor 0,, isdiverted along the clamping arrangement including line 334 and switch294. When switch 294 is opened with the elevation of operator assembly50, another clamping arrangement including diode 358 and line 360provides a current diverting path to the output 224 of mode conversiontiming function 218 in order to retain transistor Q, in a reverse biasedstate while timing function 218 is timing out the period required foroperator assembly 50 to reach its exposure mode orientation. During thisperiod, the output at line 224 will be low and, as a consequence,clamping line 360 is permitted to provide a diverting function.

When timing function 218 has timed out the move-.- ment of operatorassembly 50, output line 224 assumes a high status, thereby terminatingthe flow of current through line 360. As a consequence, biasing currentis introduced from line 234 through line 334 to forward bias transistor0,. An on status at transistor 0,, promotes a corresponding on status attransistor 0 thereby energizing line 356 from line 234.

During daylight or ambient mode operation of the camera, energization ofline 356 arms a light sensitive exposure control circuit. This circuitincludes a PNP transistor 0 the collector and emitter terminals of whichare coupled within line 362 between exposure function power line 356 andground reference line 214. The base of transistor Q is connected by aline 364 through diode 366 and bias resistor 368 to power line 214. Thusconnected, with the energization of line 356, transistor 0,, is forwardbiased to activate a light sensi tive R-C timing network within line362. This network includes a light sensitive resistor or photocell 370and a timing capacitor 372. A shunt including line 374, line 376, andswitch 378 is connected across capacitor 372. Switch 378 is opened atleast simultaneously with the commencement of opening movements ofblades 106 t and 108 of mechanism 104. Connected between photocell 370andcapacitor-372 is the input 380 of a differential comparator 382.Coupled between power line 356 and reference line 214 respectively, fromlines 384 and 386, the'output 388 of comparator 382 is normally low.This low output at line 388 remains until a voltage of predeterminedthreshold level is developed at its input 380 by the exposure regulatingcontrol function of the camera. I

An exposure interval is commenced with the simultaneous energization ofexposure function power line 356 and. de-energization of the winding 260of solenoid 144. To carry out the latter de-energization; a forwardbiasing of transistor 0,, provides for the activation of a currentdiverting line 394 extending from line 236, through diode 396 and to thecollector side of transistor Q,,. When activated, line 394 serves todivert biasing current passing through line 236 and bias resistor 238from the base'of transistor 0,. As a'result, transistor O is reversebiased into an off" status simultaneously with the energization'ofexposure fun'ction power line 356. When transistor 0, is reverse-biased,transistors 0 and Q correspondingly are reverse'biased. As resistor 0 ifturned of winding 260 of solenoid 144 is de-energized to release walkingbeam 124 for movement under the bias of spring 138. Blades 106 and 108of exposure mechanism 104 commence to open.

During the ensuing exposure interval, the output at line 388 ofdifferential comparator 382 remains low" until the timing networkincluding photocell 370 and timing capacitor 372 develops a voltagelevel at input 380 corresponding to the predetermined thresholdtriggering level of comparator 382. When this threshold level isreached, comparator 382 triggers to rapidly change the output at line388 to a high status. During the interval when the output at line 388 islow, current is permitted to pass from line 356 through a bias resistor398 to communicate with ground level through differential comparator 382at line 386. When the output at line 388 goes high" at the terminationof an exposure interval, current passes from line 356 through biasresistor 398 and diode 400 to the base of NPN transistor Q The emitterof transistor Q is connected to ground reference line 214 and itscollector is connected through line 402, bias resistor'404 and line 406to the base of a PNP transistor Q The emitter of transistor Q isconnected with logic power line 234 and its collector is connected toline 410. Line 410 is connected through a bias resistor 412 to the baseof an NPN transistor Q which functions to reactivate timing network 264.Line 410 additionally is coupled through line 414, bias resistor 416 anda diode 418 to line 236 leading, in turn, to the base of transistor Q Anexposure terminating high status at output 388 of differentialcomparator 382 causes the forward biasing of transistor 0,,. When soforward biased, transistor Q, draws the base-emitter junction oftransistor Q into a forward biased condition. As a consequence, currentflows from line 234 through line 410. Line 410, in turn, energizes line414 to cause a forward biasing of the base-emitterjunction of transistorQ As noted earlier, when transistor O is forward biased, transistors Qand Q,,, correspondingly, are forward biased to energize the winding 260of solenoid 144. This energization causes exposure mechanism 104 toclose blades 106 and 108 to terminate an exposure.

Turning to operation of the exposure control system in a flash mode asopposed to an ambient mode, with the insertion ofa flash unit as at 32within mounting 30, a switch as at 420 is closed. Closure of switch 420permits a differential comparator 422 to be energized from exposurefunction power line 356 and reference line 214, respectively, throughlines 424 and 426. The output of differential comparator 422 isconnected with a line 428 through the winding 430 of a solenoid to mainpower line 212. Winding 430 corresponds with the winding of afollow-focus solenoid 174 described in connection with FIGS. 2 6.Accordingly, the solenoid is again represented in the present figure asa dashed boundary 174. The output of differential comparator 422 at line428 is normally low and, as a consequence, winding 430 is energizedcoincidently with the energization of exposure function power line 356and simultaneous activation of comparator 422.

The input at line 432 of comparator 422 is connected to an R-C timingnetwork 434. Network 434 includes a resistor 436 and timing capacitor438 coupled within line'440 between exposure function power line 356 andground reference line 214. Network 434 is configured having a timeconstant corresponding at least with the amount of time required forblades 106 and 108 of exposure mechanism 104 to be driven under the biasof spring 138 from their fully closed position to their fully openposition. Following such time-out, the voltage level at input 432reaches the triggering level of differential comparator 422. When thisthreshold level is reached, the comparator 422 triggers to rapidlychange the output at line 428 to a high" status. As a result, winding430 of solenoid 174 is de-energized. As noted earlier in connection withFIG. 4, the plunger 192 of solenoid 174 remains extended at this pointwithin the photographic cycle, inasmuch as a detent 196 in its tipengages with and is retained at the extension 200 of walking beam 124.Consequently, beam 124 retains blades 106 and 108 in the predeterminedaperture position selected for flash firing.

The deenergization of winding 430 of solenoid 174 develops a spike orinductive surge in line 428 which is intercepted at a line 442 andintroduced to a flash firing network 444. Network 444, in turn, causesthe firing of one lamp within the flash-package 32. A circuit suited forthe function of flash firing network 444 is described in and claimed ina copending application for U.S. Pat. by J. P. Burgarella et al., Ser.No. 844,470, filed July 24, 1969 and assigned in common herewith.

During flash mode operation of the exposure control system, closure ofswitch 420 also diverts current from line 356 through a diode 446 andthrough line 364. This diversion lowers the requisite voltage droprequired to retain the base-emitter junction of transistor 0,, in aforward biased state. Transistor 0 therefore, turns of to de-energizeline 362 and effectively remove photocell 370 from the control circuit.The resistance represented by photocell 370 is substituted, how ever, bytiming resistor 946 coupled through a diode 448 to line 424. The timingnetwork operating in conjunction with the input 380 of differentialcomparator 382 now includes resistor 446, line 374 and capacitor 372.The time constant of this flash mode timing arrangement is selected incorrespondence with a typical predetermined duration of light output ofa flash source. Additionally, the timing period of the network isselected to be lengthier than that of network 434 to prevent a racecondition between the energization of solenoid winding 430 andde-energization of winding 260 of solenoid 144. Following an appropriatepredetermined flxed time-out of the flash mode exposure interval timingnetwork, the voltage level at input 380 of differential comparator 382reaches its predetermined triggering value and the output of thecomparator 382 at line 388 goes high. A high output at line 388 causestransistors 0, and 013 to be forward biased, in turn, causing theforward biasing of transistors Q Q and O to re-energize the winding 260of solenoid 144.

Returning to FIGS. 2 6, as solenoid 144 causes beam 124 to rotateagainst the bias of spring 138, the capture condition between detent 196of plunger 192 and extension 200 of beam 124 is eliminated and plunger192 returns to its retracted position under the bias of spring 194.

At the end of an exposure interval, the energized status of line 410causes a forward biasing of the baseemitter junction of transistor Q Theemitter of transistor Q is connected to ground reference power line 214and its collector is connected to line 284. When current from line 410forward biases transistor Q current from line 284 is diverted from line288 to line 214 and a forward bias at transistor 0 is removed. As aresult, the shunt about timing capacitor 268 is removed and timingnetwork 264 commences to time-out the period required for blades 106 and108 of exposure mechanism 104 to close. The output at line 276 ofdifferential comparator 270 remains low" until this exposure mechanismtiming period terminates, at which time it assumes a high" status. Whilethe output at line 276 remains high, the base-emitter junction oftransistor Q, is forward biased from along line 296 and diode 300. Aforward biased condition at transistor 0 in turn, causes transistor 0-,to be forward biased, thereby causing motor 310 to be re-energized fromline 308. This second energization of .motor 310. is utilized to cockoperator assembly 50 by driving it to its viewing mode position as wellas to power processing station 92. As the operator assembly 50 reachesits viewing mode position, switch 294 is again closed. When switch 294closes, forward biasing current otherwise directed to transistor O isdiverted through line 330, diode 332 and line 318 to reference powerline 214. When transistor Q thus is reverse biased, transistor Q isreverse biased to de-energize logic power line 234. The deenergizationof line 234 shuts down the entire circuit to terminate a photographiccycle.

Since certain changes may be made in the above described full exposurecontrol system without departing from a scope of the invention herein,it is intended that all matter contained in the description thereoforshown in the accompanying drawings shall be interpreted asillustrative and not in a limiting sense.

What is claimed is: 1. An exposure control system for photographicapparatus comprising: 7 I

means defining an optical path for transmitting light from a subject tobe photographed onto aphotographic material; means for energizing asource of artificial light when activated to illuminate said subject inaccordance with a given illumination factor; exposure regulator meanshaving a driven mode effectiveto block the passage of light along saidoptical path and a relaxation mode effective to progressively unblocksaid path to derive a predetermined variation of aperture valuethereover; electromagnetic means adjustable in accordance with saidillumination factor and selectively energizable to arrest the saidaperture value variation of said exposure regulator means to establish aselect exposure aperture; and control means for causing said exposureregulator means to'assume'said driven mode at the commencement ofaphotographic cycle of said apparatus, thence to energize saidelectromagnetic means, thence to cause said exposure regulator means toassume said relaxation mode, thence to activate said means forenergizing said source of artificial light, and thence to cause saidexposure regulator means to reassume said driven mode.

The exposure control system of claim 1 wherein: said exposureregulatormeans ismovable along given locus of travel when in saidrelaxation mode; and said electromagnetic'means is operative, whenenergized, to position a'stop within said locus of travel to arrest saidexposure regulator means.

1 3. .The exposure control system of claim 2 wherein saidelectromagnetic means includes a solenoid energizable to position saidstop within said locus of travel.

4. The exposure control system of claim 2 in which said electromagneticmeans stop and said exposure regulator means are configured to providemutual mechanical engagement when said exposure regulator means isarrested during said relaxation mode and to retain said engagement sothat said stop remains within said locus of travel in the presence of ade-energization of said electromagnetic means subsequent to saidengagement.

5. The exposure control system of claim 4 in which said electromagneticmeans stop and said exposure re'gulator means are operative to disengagesubsequent to said mechanical engagement when said exposure regulatormeans is caused to re-assume said driven mode. 6. The exposure controlsystem of claim 4 in which said electromagnetic means includes means forretracting said stop from said position from within said locus of travelwhen said electromagnetic means is deenergized and said exposureregulator means is caused to re-assume said driven mode.

7. The exposure control system of claim 4 wherein: said means definingsaid optical path includes a taking lens adjustably movable to focus theimage of said subject upon said photographic material; and

said electromagnetic means is adjustable in correspondence with saidtaking lens focusing adjustment.

8. The exposure control system of claim 1 in which:

said exposure regulator means includes blade means movable toward oneterminal position during said driven mode and toward another terminalposition during said relaxation mode; and

said control means is operative to energize said electromagnetic meansonly when said blade means has attained said driven mode terminalposition.

9. The exposure control system of claim 8 in which said control means isoperative to activate said source of artificial light only following aninterval of time commencing with said assumption of said relaxation modeand sufficient for said blade means to attain said relaxation modeterminal position.

10. A range responsive exposure control system for photographicapparatus comprising:

means defining an optical path;

exposure regulator means energizable to move in a first direction to aterminal position for occluding the passage of light along said opticalpath, and subsequently de-energizable to move along a given locus oftravel away from said terminal position for progressively varying theaperture value of said op-, tical path; solenoid driven means adjustableand energizablc for v selectively positioning a stop within thesaid'locus of travel of said regulator means; and I control meansresponsive to the'range of a given photographic subject for selectivelyadjusting and energizing said solenoid means to arrest said exposure.vregulator means during said movement along said locus of travel toestablish'an aperture value corresponding at least in part to saidrange, said solenoid means energization being carried outsubsequent tosaid movement of said exposure regulator means in said'first directioninto said terminal position and prior to said movement away from saidterminal position.

11. The exposure control system of claim 10 wherein said control meansincludes means for igniting a flash lamp when said aperture value isestablished.

12. The exposure control system of claim 10 wherein said solenoid meansincludes means for retracting said stop from said position within saidlocus of travel when said solenoid means isde-energized and saidexposure regulator means is moved in said first direction.

13. The exposure control system of claim 10 wherein:

said means defining an optical path includes a taking lens adjustivelymovable to focus the image of a photographic subject at an exposureplane; and

said control means is responsive to said adjustive movement toselectively position said solenoid driven means stop within said locusof travel.

14. The exposure control system of claim wherein said solenoid meansstop and said exposure regulator means are mutually configured toestablish a mechanical capture therebetween subsequent to said arrestand when said exposure regulator means is de-energized.

15. The exposure control system of claim 14 wherein said solenoid meansstop and said exposure regulator means are mutually configured todisengage from said mechanical capture when said exposure regulatormeans is moved in said first direction toward said terminal position.

16. An exposure control system for photographic apparatus comprising:

light source means for activating a source of artificial light toilluminate a photographic subject remotely positioned therefrom;

means defining an optical path for focusing an image of said subject atan exposure plane;

exposure mechanism means movable during a photographic cycle toward anopen terminal position to define a progressive variation of aperturevalues over said optical path and into a closed terminal positionblocking the passage of light along said optical path; 1

drive means actuable to selectively move said expo sure mechanismbetween said'terminal positions;

electromagnetically driven means selectively energizable and adjustableto arrest the said movement of said exposure mechanism means; and

, control means operative to actuate said drive means to move saidexposure mechanism means into said closed terminal position at thecommencement of a said photographic cycle,

thence to energize said electromagnetically driven means,

thence to actuate said drive means to move said exposure mechanism meanstoward said open terminal position, i i

thence to de-energize said electromagnetically driven means, and

thence to actuate said drive means to move said exposure mechanism meansinto said closed terminal position. v

17. The exposure control system of claim 16 in which:

said drive means includes spring means for biasing said exposuremechanism means to move toward said open terminal position.

l8.'The exposure control system of claim 16 wherein:

said drive means is operative to movesaid exposure mechanism means fromsaid closed terminal position into said open terminal position within apredetermined interval of time; and

said control means is operative to de-energize said electromagneticallydriven means following a period of time commencing with said actuationcausing said movement of said exposure mechanism means toward said openterminal position and extending at least as long as said predeterminedinterval.

19. The exposure control system of claim 18 wherein:

said drive means includes spring means for biasing said exposuremechanism means to move toward said open terminal position.

20. The exposure control system ofclaim 16 wherein:

said exposure mechanism means is movable along a given locus of traveltoward said open terminal position; and

said electromagnetically driven means is energizable to position a stopwithin said locus of travel to arrest said exposure mechanism means todefine said select aperture value.

21. The exposure control system of claim 20 wherein saidelectromagnetically driven means includes a solenoid energizable toposition said stop within said locus of travel.

22. The exposure control system of claim 20 in which:

said electromagnetically driven means includes a solenoid energizable toposition said stop within said locus of travel of said exposuremechanism means; and

said control means is operative to deenergize said solenoid a selectperiod of time following said actuation of said drive means to move saidexposure mechanism means toward said open terminal position andtoactivate said light source means in response to said de-energization.

23. An exposure control system for a single lens reflex camera having aviewing mode permitting the viewing of the image ofa scene before andafter an exposure, and an exposure mode for exposing photosensitivematerial, comprising:

means defining an optical path for exposing said photosensitive materialat an exposure plane to light from said scene;

exposure mechanism means movable toward an open terminal position todefine a time dependent progressive variation of exposure aperturevalues over said optical path, and movable into a closed terminalposition blocking the passage of light along said optical path;

spring means for biasing said exposure mechanism means to move towardsaid open terminal position; drive means energizable to cause saidexposure mechanism means to move into said closed terminal position; Ielectromagnetic means energizable and adjustable to arrest the saidmovement of said exposure mechanism means under said spring means biasto'establish a select exposure aperture value over said optical pathcorresponding with the-level of illumination anticipated from anartificial light source; reflex operator means actuable to move betweenone position blocking the exposure of photosensitive material when saidcamera'is injisaid viewing mode and another position permitting theexposure of said photosensitive material when said camera is in saidexposure mode; and control means operative to energize said drive meansto move said exposure mechanism means into said closed terminal positionat the commencement of a said photographic cycle,

thence to actuate said reflex operator means to move into said otherposition and to energize said elec-: tromagnetic means,

thence to initially de-energize said drive means to cause said exposuremechanism means movement from said closed tenninal position under saidspring means bias,

thence to activate said artificial light source after said selectexposure aperture is established,

thence to energize said drive means to move said exposure mechanismmeans into said closed terminal position,

thence to actuate said reflex operator means to move into said oneposition, and

thence to de-energize said drive means to cause said exposure mechanismmeans movement from said closed terminal position under said springmeans bias.

24. The exposure control system of claim 23 in which said control meansis operative to activate said artificial light source in response to ade-energization of said electromagnetic means.

25. The exposure control system of claim 23 wherein:

said exposure mechanism means is movable along a given locus of traveltoward said open terminal position; and

said electromagnetic means is energizable to position a stop within saidlocus of travel to arrest said exposure mechanism means to define saidselect exposure aperture value. I

26. The exposure control system of claim 25 wherein:

said drive means is operative to move said exposure mechanism means fromsaid closed terminal position into said open terminal position within apredetermined interval of time; and

said control means is operative to de-energize said electromagneticmeans following a period of time commencing with the said initialde-energization of said drive means and extending atvleast as long assaid predetermined interval.

27. The exposure control system of claim 25 wherein said electromagneticmeans includes a solenoid energizable to position said stop within saidlocus of travel.

28. The exposure control mechanism of claim 27 in which saidelectromagnetic means stop and saidexposure mechanism means are mutuallyconfigured to establish a mechanical capture therebetween subsequent tosaid arrest and when said exposure mechanism means is de-energized.

29. The exposure control system of claim 28 in which saidelectromagnetic means stop and said exposure mechanism means areoperative to disengage from said mechanical capture when said exposuremechanism means is moved by said drivemeans toward said closed terminalposition. Y 7 1 30. The exposure control system of claim 29 in whichsaid electromagnetic means includes means for retracting said, stop fromsaid position within said locus of travel when said electromagneticmeans is de-energized and said exposure mechanism means is moved towardsaid closed terminal position.

31. The exposure control system of claim 30 wherein:

said means defining an optical path includes a taking lens adjustable tofocus the image of said scene at said exposure plane; and

said electromagnetic means ia adjustable in correspondence with focusadjustment of the said takinglens.

32. An exposure control system for photographic apparatus operative inan ambient mode responsive to the light level of a scene and in flashmode responsive to the level of flash lamp illumination anticipated atsaid scene comprising:

means defining an optical path for exposing a photosensitive material;exposure mechanism means movable toward an open terminal position todefine a time dependent progressive variation of exposure aperturevalues over said optical path, and movable into a closed terminalposition blocking the passage of light along said optical path; meansfor biasing said exposure mechanism means to move toward said openterminal position;

electromagnetic drive means energizable to cause said exposure mechanismmeans to assume said closed terminal position, de-energizable to causesaid movement under said bias from said closed terminal position towardsaid open terminal position to initiate an exposure and, subsequently,energizable to move said exposure mechanism means into said closedterminal position to terminate said exposure; electromagnetically drivenmeans energizable and adjustable to arrestthe said movement of saidexposure mechanism means under said bias to establish a select exposureaperture value over said optical path corresponding with saidanticipated level of flash lamp illumination; 5 switch means actuable tocause said exposure control system to operate in said flash mode; and 5control circuit means for selectively energizing and de-energizing saidelectromagnetic drive means and including: light sensitive cireuitmeansresponsive during a said ambient mode exposure to said progressivevariation of said exposure apertures and to the level'of said scenelight in accordance with the sensitometric properties of saidphotosensitive material for controlling the said energization of saidelectromagnetic drive means to cause'said exposure termination; andflash mode circuit means operative only in response to actuation of saidswitch means for energizing said electromagnetically driven means toestablish said select exposure aperture, for de-activating said scenelight responsiveness of said light sensitive circuit means and forcontrolling the said'energization of said electromagnetic drive means tocause said exposure termination following illumination of said scenefrom such flash lamp. 33 The exposure control system of claim 32 whereinsaid flash'mode circuit means is operative to energize saidelectromagnetic drive means to cause said exposure termination apredetermined fixed interval of time following the saidexposure'initiating de-energization thereof. r a

34. The exposure control system of claim 32 wherein said means definingan optical path includes a taking lens adjustable to focus the image ofsaid scene upon said photosensitive material; and

said electromagnetically driven means is automatically adjustable incorrespondence withthe adjustment of said taking lens. I

35. The exposure control system of claim 32 wherein:

said exposure mechanism means is movable along a given locus of traveltoward said open terminal position; and i Z said electromagneticallydriven means is operative in response to said energization to position astop within said locus of travel to arrest said exposure mechanism meansto establish said select exposure aperture.

36. The exposure control system of claim 35 wherein said stop and saidexposure mechanism means are mutually configured to establish amechanical capture therebetween subsequent to said arrest and when saidexposure mechanism means is moved under said bias.

37. The exposure control system of claim 35 wherein said stop and saidexposure mechanism means are mutually configured to engage in a mannerestablishing a mechanical capture when said exposure mechanism means isarrested during said movement under said bias, and to disengage whensaid exposure mechanism means is moved toward said closed terminalposition to terminate a said exposure.

38. The exposure control system of claim 37 in which saidelectromagnetically driven means includes means for retracting said stopfrom said position within said locus of travel when saidelectromagnetically driven means is de-energized and said exposuremechanism means is moved toward said closed terminal position.

39. The exposure control system of claim 37 in which:

said biasing means is operative to move said exposure mechanism meansbetween said terminal positions within a predetermined interval of time;and

said flash mode circuit means is operative to energize saidelectromagnetically driven means prior to said movement of said exposuremechanism means under said bias and to de-energize saidelectromagnetically driven means following a time delay commencing withthe de-energization of said electromagnetic drive means and extending atleast as long as said predetermined interval.

40. The exposure control system of claim 39 wherein said flash modecircuit means is operative to cause illumination by such a flash lamp inresponse to an inductive pulse resulting from the de-energization ofsaid clectromagnetically driven means.

41. The exposure control system of claim 39 wherein said flash modecircuit means is operative to energize said electromagnetic drive meansto cause said exposure termination a predetermined fixed interval oftime following the said exposure initiating de-energization thereof,said predetermined fixed interval being selected to be longer induration than said electromagnetically driven means de-energization timedelay.

42 An exposure control system for photographic apparatus comprising: v

means defining an optical path for transmitting light from a subject tobe photographed onto a photorest the aperture variation of said exposureregulator means to establish a select exposure aperture; and

control means for selectively activating said means for energizing saidsource of light and operative to cause said exposure regulator means toassume said driven mode at the commencement of a photographic cycle ofsaid apparatus,

thence to energize said electromagnetic means,

thence to cause said exposure regulator means to assume said relaxationmode,

thence to de-energize said electromagnetic means,

and thence to cause said exposure regulator means to assume said drivenmode. 43. The exposure control system of claim 1 in which said controlmeans is operative to de-energize said electromagnetic means at thetermination of a predetermined interval following the said assumption ofsaid relaxation mode by said exposure regulator means.

44. The exposure control system of claim 42 in which said control meansisoperative to activate said means for energizing said source ofartificial light in response to the said de-energization of saidelectromagnetic means. I 45. The exposure control system of claim 43 inwhich said control means is operative to activate said means forenergizing said source of artificial light in response tosaidelectromagnetic means de-energization.

46. The exposure control system of claim 45 in which saidelectromagnetic means includes stop means engageable with said exposureregulator means, said stop means being configured to remain in saidengagement until said exposure regulator means is caused to reassumesaid driven mode.

47. The exposure control system of claim 42 in which:

said exposure regulator means includes blade means movable toward oneterminal position during said driven mode and toward another terminalposition during said relaxation modeaand said control means is operativeto energize said electromagnetic means only when said blade means hasattained said driven mode terminal position.

48. The exposure control system of claim 47- in which: a

said control means is operative to activate said source of artificiallight only following an interval ofv time commencing with saidassumption of said relaxation mode and sufficient for said blade meansto 'attain said relaxation mode terminal p o'sition.

49. The exposure control-systemof claim48 inwhich said control means isoperative to de-energize said electromagnetic means at the terminationof a predetermined interval following the said assumption of said retosaid electromagnetic means de-energization.

t t i i

1. An exposure control system for photographic apparatus comprising:means defining an optical path for transmitting light from a subject tobe photographed onto a photographic material; means for energizing asource of artificial light when activated to illuminate said subject inaccordance with a given illumination factor; exposure regulator meanshaving a driven mode effective to block the paSsage of light along saidoptical path and a relaxation mode effective to progressively unblocksaid path to derive a predetermined variation of aperture valuethereover; electromagnetic means adjustable in accordance with saidillumination factor and selectively energizable to arrest the saidaperture value variation of said exposure regulator means to establish aselect exposure aperture; and control means for causing said exposureregulator means to assume said driven mode at the commencement of aphotographic cycle of said apparatus, thence to energize saidelectromagnetic means, thence to cause said exposure regulator means toassume said relaxation mode, thence to activate said means forenergizing said source of artificial light, and thence to cause saidexposure regulator means to re-assume said driven mode.
 2. The exposurecontrol system of claim 1 wherein: said exposure regulator means ismovable along a given locus of travel when in said relaxation mode; andsaid electromagnetic means is operative, when energized, to position astop within said locus of travel to arrest said exposure regulatormeans.
 3. The exposure control system of claim 2 wherein saidelectromagnetic means includes a solenoid energizable to position saidstop within said locus of travel.
 4. The exposure control system ofclaim 2 in which said electromagnetic means stop and said exposureregulator means are configured to provide mutual mechanical engagementwhen said exposure regulator means is arrested during said relaxationmode and to retain said engagement so that said stop remains within saidlocus of travel in the presence of a de-energization of saidelectromagnetic means subsequent to said engagement.
 5. The exposurecontrol system of claim 4 in which said electromagnetic means stop andsaid exposure regulator means are operative to disengage subsequent tosaid mechanical engagement when said exposure regulator means is causedto re-assume said driven mode.
 6. The exposure control system of claim 4in which said electromagnetic means includes means for retracting saidstop from said position from within said locus of travel when saidelectromagnetic means is de-energized and said exposure regulator meansis caused to re-assume said driven mode.
 7. The exposure control systemof claim 4 wherein: said means defining said optical path includes ataking lens adjustably movable to focus the image of said subject uponsaid photographic material; and said electromagnetic means is adjustablein correspondence with said taking lens focusing adjustment.
 8. Theexposure control system of claim 1 in which: said exposure regulatormeans includes blade means movable toward one terminal position duringsaid driven mode and toward another terminal position during saidrelaxation mode; and said control means is operative to energize saidelectromagnetic means only when said blade means has attained saiddriven mode terminal position.
 9. The exposure control system of claim 8in which said control means is operative to activate said source ofartificial light only following an interval of time commencing with saidassumption of said relaxation mode and sufficient for said blade meansto attain said relaxation mode terminal position.
 10. A range responsiveexposure control system for photographic apparatus comprising: meansdefining an optical path; exposure regulator means energizable to movein a first direction to a terminal position for occluding the passage oflight along said optical path, and subsequently de-energizable to movealong a given locus of travel away from said terminal position forprogressively varying the aperture value of said optical path; solenoiddriven means adjustable and energizable for selectively positioning astop within the said locus of travel of said regulator means; andcontrol means responsive to the range of a given photographic subjectfor selectively adjusting and energizing said solenoid means to arrestsaid exposure regulator means during said movement along said locus oftravel to establish an aperture value corresponding at least in part tosaid range, said solenoid means energization being carried outsubsequent to said movement of said exposure regulator means in saidfirst direction into said terminal position and prior to said movementaway from said terminal position.
 11. The exposure control system ofclaim 10 wherein said control means includes means for igniting a flashlamp when said aperture value is established.
 12. The exposure controlsystem of claim 10 wherein said solenoid means includes means forretracting said stop from said position within said locus of travel whensaid solenoid means is de-energized and said exposure regulator means ismoved in said first direction.
 13. The exposure control system of claim10 wherein: said means defining an optical path includes a taking lensadjustively movable to focus the image of a photographic subject at anexposure plane; and said control means is responsive to said adjustivemovement to selectively position said solenoid driven means stop withinsaid locus of travel.
 14. The exposure control system of claim 10wherein said solenoid means stop and said exposure regulator means aremutually configured to establish a mechanical capture therebetweensubsequent to said arrest and when said exposure regulator means isde-energized.
 15. The exposure control system of claim 14 wherein saidsolenoid means stop and said exposure regulator means are mutuallyconfigured to disengage from said mechanical capture when said exposureregulator means is moved in said first direction toward said terminalposition.
 16. An exposure control system for photographic apparatuscomprising: light source means for activating a source of artificiallight to illuminate a photographic subject remotely positionedtherefrom; means defining an optical path for focusing an image of saidsubject at an exposure plane; exposure mechanism means movable during aphotographic cycle toward an open terminal position to define aprogressive variation of aperture values over said optical path and intoa closed terminal position blocking the passage of light along saidoptical path; drive means actuable to selectively move said exposuremechanism between said terminal positions; electromagnetically drivenmeans selectively energizable and adjustable to arrest the said movementof said exposure mechanism means; and control means operative to actuatesaid drive means to move said exposure mechanism means into said closedterminal position at the commencement of a said photographic cycle,thence to energize said electromagnetically driven means, thence toactuate said drive means to move said exposure mechanism means towardsaid open terminal position, thence to de-energize saidelectromagnetically driven means, and thence to actuate said drive meansto move said exposure mechanism means into said closed terminalposition.
 17. The exposure control system of claim 16 in which: saiddrive means includes spring means for biasing said exposure mechanismmeans to move toward said open terminal position.
 18. The exposurecontrol system of claim 16 wherein: said drive means is operative tomove said exposure mechanism means from said closed terminal positioninto said open terminal position within a predetermined interval oftime; and said control means is operative to de-energize saidelectromagnetically driven means following a period of time commencingwith said actuation causing said movement of said exposure mechanismmeans toward said open terminal position and extending at least as longas said predetermined interval.
 19. The exposure control system of claim18 wherein: said drive means includes spring means for biasing saidexposure mechanism means to move toward said open terminal position. 20.The exposure control syStem of claim 16 wherein: said exposure mechanismmeans is movable along a given locus of travel toward said open terminalposition; and said electromagnetically driven means is energizable toposition a stop within said locus of travel to arrest said exposuremechanism means to define said select aperture value.
 21. The exposurecontrol system of claim 20 wherein said electromagnetically driven meansincludes a solenoid energizable to position said stop within said locusof travel.
 22. The exposure control system of claim 20 in which: saidelectromagnetically driven means includes a solenoid energizable toposition said stop within said locus of travel of said exposuremechanism means; and said control means is operative to de-energize saidsolenoid a select period of time following said actuation of said drivemeans to move said exposure mechanism means toward said open terminalposition and to activate said light source means in response to saidde-energization.
 23. An exposure control system for a single lens reflexcamera having a viewing mode permitting the viewing of the image of ascene before and after an exposure, and an exposure mode for exposingphotosensitive material, comprising: means defining an optical path forexposing said photosensitive material at an exposure plane to light fromsaid scene; exposure mechanism means movable toward an open terminalposition to define a time dependent progressive variation of exposureaperture values over said optical path, and movable into a closedterminal position blocking the passage of light along said optical path;spring means for biasing said exposure mechanism means to move towardsaid open terminal position; drive means energizable to cause saidexposure mechanism means to move into said closed terminal position;electromagnetic means energizable and adjustable to arrest the saidmovement of said exposure mechanism means under said spring means biasto establish a select exposure aperture value over said optical pathcorresponding with the level of illumination anticipated from anartificial light source; reflex operator means actuable to move betweenone position blocking the exposure of said photosensitive material whensaid camera is in said viewing mode and another position permitting theexposure of said photosensitive material when said camera is in saidexposure mode; and control means operative to energize said drive meansto move said exposure mechanism means into said closed terminal positionat the commencement of a said photographic cycle, thence to actuate saidreflex operator means to move into said other position and to energizesaid electromagnetic means, thence to initially de-energize said drivemeans to cause said exposure mechanism means movement from said closedterminal position under said spring means bias, thence to activate saidartificial light source after said select exposure aperture isestablished, thence to energize said drive means to move said exposuremechanism means into said closed terminal position, thence to actuatesaid reflex operator means to move into said one position, and thence tode-energize said drive means to cause said exposure mechanism meansmovement from said closed terminal position under said spring meansbias.
 24. The exposure control system of claim 23 in which said controlmeans is operative to activate said artificial light source in responseto a de-energization of said electromagnetic means.
 25. The exposurecontrol system of claim 23 wherein: said exposure mechanism means ismovable along a given locus of travel toward said open terminalposition; and said electromagnetic means is energizable to position astop within said locus of travel to arrest said exposure mechanism meansto define said select exposure aperture value.
 26. The exposure controlsystem of claim 25 wherein: said drive means is operative to move saidexposure mechAnism means from said closed terminal position into saidopen terminal position within a predetermined interval of time; and saidcontrol means is operative to de-energize said electromagnetic meansfollowing a period of time commencing with the said initialde-energization of said drive means and extending at least as long assaid predetermined interval.
 27. The exposure control system of claim 25wherein said electromagnetic means includes a solenoid energizable toposition said stop within said locus of travel.
 28. The exposure controlmechanism of claim 27 in which said electromagnetic means stop and saidexposure mechanism means are mutually configured to establish amechanical capture therebetween subsequent to said arrest and when saidexposure mechanism means is de-energized.
 29. The exposure controlsystem of claim 28 in which said electromagnetic means stop and saidexposure mechanism means are operative to disengage from said mechanicalcapture when said exposure mechanism means is moved by said drive meanstoward said closed terminal position.
 30. The exposure control system ofclaim 29 in which said electromagnetic means includes means forretracting said stop from said position within said locus of travel whensaid electromagnetic means is de-energized and said exposure mechanismmeans is moved toward said closed terminal position.
 31. The exposurecontrol system of claim 30 wherein: said means defining an optical pathincludes a taking lens adjustable to focus the image of said scene atsaid exposure plane; and said electromagnetic means is adjustable incorrespondence with focus adjustment of the said taking lens.
 32. Anexposure control system for photographic apparatus operative in anambient mode responsive to the light level of a scene and in flash moderesponsive to the level of flash lamp illumination anticipated at saidscene comprising: means defining an optical path for exposing aphotosensitive material; exposure mechanism means movable toward an openterminal position to define a time dependent progressive variation ofexposure aperture values over said optical path, and movable into aclosed terminal position blocking the passage of light along saidoptical path; means for biasing said exposure mechanism means to movetoward said open terminal position; electromagnetic drive meansenergizable to cause said exposure mechanism means to assume said closedterminal position, de-energizable to cause said movement under said biasfrom said closed terminal position toward said open terminal position toinitiate an exposure and, subsequently, energizable to move saidexposure mechanism means into said closed terminal position to terminatesaid exposure; electromagnetically driven means energizable andadjustable to arrest the said movement of said exposure mechanism meansunder said bias to establish a select exposure aperture value over saidoptical path corresponding with said anticipated level of flash lampillumination; switch means actuable to cause said exposure controlsystem to operate in said flash mode; and control circuit means forselectively energizing and de-energizing said electromagnetic drivemeans and including: light sensitive circuit means responsive during asaid ambient mode exposure to said progressive variation of saidexposure apertures and to the level of said scene light in accordancewith the sensitometric properties of said photosensitive material forcontrolling the said energization of said electromagnetic drive means tocause said exposure termination; and flash mode circuit means operativeonly in response to actuation of said switch means for energizing saidelectromagnetically driven means to establish said select exposureaperture, for de-activating said scene light responsiveness of saidlight sensitive circuit means and for controlling the said energizationof said electromagnetic drive means to cause said exposure terminationfollowing illuMination of said scene from such flash lamp.
 33. Theexposure control system of claim 32 wherein said flash mode circuitmeans is operative to energize said electromagnetic drive means to causesaid exposure termination a predetermined fixed interval of timefollowing the said exposure initiating de-energization thereof.
 34. Theexposure control system of claim 32 wherein said means defining anoptical path includes a taking lens adjustable to focus the image ofsaid scene upon said photosensitive material; and saidelectromagnetically driven means is automatically adjustable incorrespondence with the adjustment of said taking lens.
 35. The exposurecontrol system of claim 32 wherein: said exposure mechanism means ismovable along a given locus of travel toward said open terminalposition; and said electromagnetically driven means is operative inresponse to said energization to position a stop within said locus oftravel to arrest said exposure mechanism means to establish said selectexposure aperture.
 36. The exposure control system of claim 35 whereinsaid stop and said exposure mechanism means are mutually configured toestablish a mechanical capture therebetween subsequent to said arrestand when said exposure mechanism means is moved under said bias.
 37. Theexposure control system of claim 35 wherein said stop and said exposuremechanism means are mutually configured to engage in a mannerestablishing a mechanical capture when said exposure mechanism means isarrested during said movement under said bias, and to disengage whensaid exposure mechanism means is moved toward said closed terminalposition to terminate a said exposure.
 38. The exposure control systemof claim 37 in which said electromagnetically driven means includesmeans for retracting said stop from said position within said locus oftravel when said electromagnetically driven means is de-energized andsaid exposure mechanism means is moved toward said closed terminalposition.
 39. The exposure control system of claim 37 in which: saidbiasing means is operative to move said exposure mechanism means betweensaid terminal positions within a predetermined interval of time; andsaid flash mode circuit means is operative to energize saidelectromagnetically driven means prior to said movement of said exposuremechanism means under said bias and to de-energize saidelectromagnetically driven means following a time delay commencing withthe de-energization of said electromagnetic drive means and extending atleast as long as said predetermined interval.
 40. The exposure controlsystem of claim 39 wherein said flash mode circuit means is operative tocause illumination by such a flash lamp in response to an inductivepulse resulting from the de-energization of said electromagneticallydriven means.
 41. The exposure control system of claim 39 wherein saidflash mode circuit means is operative to energize said electromagneticdrive means to cause said exposure termination a predetermined fixedinterval of time following the said exposure initiating de-energizationthereof, said predetermined fixed interval being selected to be longerin duration than said electromagnetically driven means de-energizationtime delay.
 42. An exposure control system for photographic apparatuscomprising: means defining an optical path for transmitting light from asubject to be photographed onto a photographic material; means forenergizing a source of artificial light when activated to illuminatesaid subject in accordance with a given illumination factor; exposureregulator means having a driven mode effective to block the passage oflight along said optical path and a relaxation mode effective toprogressively unblock said path to derive a predetermined aperturevariation thereover; electromagnetic means adjustable in accordance withsaid illumination factor and energizable to arrest the aperturevariation of said exposure regulator means to establish a Selectexposure aperture; and control means for selectively activating saidmeans for energizing said source of light and operative to cause saidexposure regulator means to assume said driven mode at the commencementof a photographic cycle of said apparatus, thence to energize saidelectromagnetic means, thence to cause said exposure regulator means toassume said relaxation mode, thence to de-energize said electromagneticmeans, and thence to cause said exposure regulator means to assume saiddriven mode.
 43. The exposure control system of claim 1 in which saidcontrol means is operative to de-energize said electromagnetic means atthe termination of a predetermined interval following the saidassumption of said relaxation mode by said exposure regulator means. 44.The exposure control system of claim 42 in which said control means isoperative to activate said means for energizing said source ofartificial light in response to the said de-energization of saidelectromagnetic means.
 45. The exposure control system of claim 43 inwhich said control means is operative to activate said means forenergizing said source of artificial light in response to saidelectromagnetic means de-energization.
 46. The exposure control systemof claim 45 in which said electromagnetic means includes stop meansengageable with said exposure regulator means, said stop means beingconfigured to remain in said engagement until said exposure regulatormeans is caused to re-assume said driven mode.
 47. The exposure controlsystem of claim 42 in which: said exposure regulator means includesblade means movable toward one terminal position during said driven modeand toward another terminal position during said relaxation mode; andsaid control means is operative to energize said electromagnetic meansonly when said blade means has attained said driven mode terminalposition.
 48. The exposure control system of claim 47 in which: saidcontrol means is operative to activate said source of artificial lightonly following an interval of time commencing with said assumption ofsaid relaxation mode and sufficient for said blade means to attain saidrelaxation mode terminal position.
 49. The exposure control system ofclaim 48 in which said control means is operative to de-energize saidelectromagnetic means at the termination of a predetermined intervalfollowing the said assumption of said relaxation mode by said exposureregulator means.
 50. The exposure control system of claim 49 in whichsaid control means is operative to activate said means for energizingsaid source of artificial light in response to said electromagneticmeans de-energization.